Carburizing furnace



19, 1932. H w ER I CARBURIZING FURNACE Filed July 11, 1930 patented July19, 1 932 UNITED STATES reams?! PATENT HAROLD W. FLETCHER, F HOUSTON,TEXAS, ASSIGNOR TO HUGHES TOOL COMPANY, HOUSTON, TEXAS, A CORPORATION OFTEXAS GARJB'U'RIZING FURNACE Application filed July 11,

My invention relates to furnaces for the I heat treatment of metals, andis particularly adapted for use in treating tools and similar objects byheat in the presence of a carburizing atmosphere.

is an object of my invention to provide means to maintain within thefurnace a temperature such as is necessary for the proper treatment ofthe tools through the use of a heating unit entirely within the furnace.

It is another object of the invention to provide means for circulatingthe carburizing material constantly through and against the tools to behardened so that said tools may be uniformly exposed to contact with thecarburizing materials.

I also desire to form a simple and compact structure of heat treatingfurnace in which the metals or tools to be treated may be readi- 1yintroduced therein for treatment and also readily removed aftertreatment.

Referring to the drawing herewith, I have shown in Fig. l a centralvertical section through a furnace constructed in accordance with myinvention. "Fig.2 isa. transverse .section taken on the plane 22 of Fig.1.

I have shown my furnace as cylindrical in general outline, although itis to .be'understood that, it may be made in anydes red shape or form.There is an outer shell 1 having vertical sides and a circular base 2which is adapted to contain a heat insulating material 3. Saidinsulating material may be of a general fibrous construction such asasbestos or 5 any similar well known type of heat insulating materialunaffected by ordinary high temperatures.

Within the outer wall 3 of heat insulating material is an inner wall orlining 4 of firebrick or other similar heat resisting material of arigid nature, which forms an interior linin for the furnace. The lowersection of the rebrick shown at 5 is-formed' with a series of recesses 6therein to receive'the lower 5 ends of guide members 7. Said guidemembers. may be of angle iron construction, sup ported at their upperends by connection with a plate 8 resting upon the upper end of a ring 9of firebrick. Between the guide members? and the wall 1980. Serial No.467,203.

4 of the furnace is a space within which I place my heating unitindicated at 10, said heating unit is preferably an electrical heatingunit made'of strips of electricalresisting material formed in ribbons ofmetal extendmg in loops up and down the face of the wall 4. This ribbonof material is connected at" and have an outer shell indicated at 17.The

ring 16 extends downwardly below the ring 15 and is spaced slightly fromthe guide members 7. The metal sheath 17 on the ring 15 has radiallyextending plates 18 through which screw rods 19 may project. Said rodsare shown as pivotally secured at 20 to the outer heat insulating wall 1and extend upwardly through the plate 18v and have thumbnuts '21 ontheir upper ends.

In the carburizing operation gas is introduced into the furnace-by Wayof a pipe 22 extending into the inner ring 16 for a short distance andconnected with a central passage 23 which extends downwardly through thecover plate and furnishes space for the passage ofxa carburizing gas,and also receives a shaft 24 upon a motor 25 mounted on the-upper sideof the cover plate. The passage23 is closed below the motor 25 by aplate 26. which largely obviates the escape of gas around the motorshaft. On the lower end of the motor shaft and within the furnace is afan 27.

Spaced slightly below the fan 27 is an annular plate 29 supported on.the lower side of the cover plate and allowing the fan to circulate thegas in the furnace laterally around the outer edge of the plate 29. Saidgas may pass downwardly through the furnace and furnace.

upwardly through the opening in the plate 99 to be again circulatedoutwardly as before. There is a valve 31 in the gas line to regulate theamount of gas entering the I find it necessary to provide a vent for theescape of the used gas from the furnace, such a vent is shown at 32. Itextends upwardly through the cover plate and connects with the line 33through which the gas may be carried away.

To determine the temperature of the furnace, a thermocouple 34 isprovided. This structure being well known in the art, no furtherdescription is necessary.

For the handling of tools ormetal parts to be carburized, I have shown abasket 35 which may be made of any desired metal adapted to resist theaction of heat and in which the tools to be carburized may be inserted.

In the operation of the device, the tools to be carburized will beplaced in a basket and lowered into the furnace. The cover plate willthen be placed in position and latched firmly against the upper wall ofthe furnace so that no gas may escape. The heating element will then beturned on to bring the temperature within the furnace to the properpoint. Gas will then be introduced through the line 31 to the furnace,and the motor 25 will be started to operate the fan 27 and circulate thecarburizing gas through the basket and the tools therein. A slightamount of gas may gradually escape through the pipe 33 to allow for theentrance of new gas as the process is carried out. The gas which is usedmay be methane or other hydrocarbon gas as may be desired in theparticular treatment of the charge of tools in the basket. When theprocess has been carried on for sufficient length of time to properlytreat the tools, the entrance of gas may be discontinned, the motorstopped, and the basket with the tools therein removed.

The advantages of this construction lie in the fact that the heating ofthe furnace may be carried on with the heating element entirely withinthe inner chamber of the furnace. Furthermore the manner in which thecarburizing gas is circulated through the tools during their treatmentenables me to obtain a uniform contact of the gas with all of the toolsbeing treated so that uniform and furnace, a shaft for. said fanextending through said inlet, means to rotate said fan, and a vent forthe gas from said furnace.

In testimony whereof, I hereunto aflix my signature, this 7th day ofJuly, A. D. 1930.

HAROLD W. FLETCHER.

fan on said door and a vent from said furnace for spent gas.

2. A furnace, a heating unit within the same, an inlet opening for gasto said furnace, a rotating fan to circulate the gas in said

